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Po Gyu Park,Kyu-Tae Kim,Mun-Seog Kim,Vladlen Ya. Shifrin,Wan-Seop Kim,Young Gyun Kim 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.4
A system for automatic compensation of the Earth’s magnetic field and precise generation of a low magnetic-flux-density was developed on the basis of Cs and He-Cs atomic-magnetic-resonance magnetometers in nonmagnetic facilities. The permanent and time-varying components of the Earth’s magnetic field were compensated for by using Helmholtz coils and a Cs magnetic-field controller. Also, a thermo-compensation was applied to reduce drift of the magnetic flux density in the coil. A precision quartz solenoid and atomic-magnetic-resonance current source were used to generate a standard magnetic flux density. The standard deviation of the generated magnetic flux density was 0.02 nT for 1 to 60 s with a drift of the Earth’s magnetic field of 0.1 nT for 1 h in the range of 20 μT to 1.2 mT.
Bilateral comparison of DC magnetic flux density between NML-SIRIM and KRISS (P1-APMP.EM-S13)
Park, Po Gyu,Kim, Wan-Seop,Gyun Kim, Young,Mohd Amran, Shakirah BUREAU INTERNATIONAL DES POIDS ET MESURES 2014 METROLOGIA -BERLIN- Vol.51 No.-
<P>A bilateral comparison of magnetic flux density has been performed between Korea Research Institute of Standards and Science (KRISS) and National Metrology Laboratory, SIRIM (NML-SIRIM), and registered as APMP.EM-S13 in the BIPM key comparison database. This comparison was piloted by KRISS and the results of the NML-SIRIM were linked to those of the CCEM.M-K1 key comparison through KRISS. The mean value of the coil constant and the uncertainty of the mean reported by both laboratories were used in the calculation of the degree of equivalence (DOE).</P><P>Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.</P><P>The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).</P>
박포규(Po Gyu Park),김영균(Young Gyun Kim),김완섭(Wan-Seop Kim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
본 논문은 자기장을 이용하여 전류를 안정화시켜 정밀전류를 발생 시킬 수 있는 장치에 관한 연구이다. 일반적으로 전류를 안정화 시키는 방법은 전류회로에 직렬로 저항을 연결하여 저항 양단에 유도되는 전압을 측정하여 전류를 제어하는 방법을 많이 사용한다. 그러나 이 방법은 정밀한 전류를 제어하기 위하여 직렬로 연결되는 저항값이 커야하며, 또한 전류에 의해 발생되는 열로 인해 저항값이 증가하기 때문에 정밀한 제어가 어렵다. 이러한 단점을 보완 할 수 있는 방법으로 전류회로에 직렬로 코일을 연결하여 전류가 변화면 코일속에 자기장이 변화는 원리를 이용하여 전류를 안정화시켜 정밀전류를 발생 할 수 있다. 본 연구에서는 저자기장 국가표준 확립 및 물리고유상수인 양성자 자기회전비율 측정을 위해 원자자기공명 방법을 이용하여 직류전류를 1 A 범위에서 0.1 ㎂ 수준으로 안정화 시켰다.
브라운관의 자기장 영향 분석용 저자기장 제어 장치의 설계 및 제작
박포규(Po Gyu Park),김영균(Young Gyun Kim),신석우(Suk Woo Shin),최형호(Hyung Ho Choi),김태익(Tae-Ik Kim),정동근(Dong-Keun Jung) 한국자기학회 2003 韓國磁氣學會誌 Vol.13 No.6
We have developed the quality analysis system for magnetic field effect of cathode-ray tube that is used a monitor, TV, medical appliance. We designed, constructed the large 3-axis square coil (2 m length) system for the generation of 3-component magnetic field using power supply, magnetometer, computer below 0.2 mT range. The coil constant is 30.31 μT, 29.73 μT, 30.51 μT for the X, Y,, Z axis square coil respectively. The magnetic field resolution was 0.01 T. The uniformity of magnetic field was measured within 1 % in the range of 12 ㎝.
박포규(Po Gyu Park),김영균(Young Gyun Kim),김완섭(Wan-Seop Kim),기문석(Mun-Seok Kim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.4
교류 자기장의 정밀측정, 자기장 측정기의교정 및 관련 시험 등을 지원하기 위해 교류자기장 표준장치를 개발하였다. 주파수에 따른 확장불확도(expanded uncertainty, 2 ?)는 1 ㎑ 이하에 서 0.16 %, 1 ㎑ ~ 5 ㎑ 에서 0.26 %, 5 ㎑ ~ 20 ㎑ 에서 0.44 % 이었다. 측정결과에 대한 국제적 신뢰성 및 상호인증을 확보하기 위하여 핵심측정표준 국제비교(international key comparison)에 참여하였으며, 또한 측정능력, 교정 및 시험방법 등에 대한 국제적 전문가로부터 평가(peer review)를 수감하였다. 따라서 한국표준과학연구원 (KRISS)에서 교정 및 측정한 결과에 대해서는 국제적 상호인증을 받을 수 있다.
Irreversible Magnetization of MgB₂ Superconductor
Mun-Seog Kim,Kyu-Tae Kim,Wan-Seop Kim,Po Gyu Park,Kyu Won Lee,Sung-Ik Lee 한국자기학회 2005 Journal of Magnetics Vol.10 No.4
We report the magnetic-field dependence of the irreversible magnetization of binary superconductor MgB₂. For the temperature region of T < 0.9Tc, the contribution of the bulk pinning to the magnetization overwhelms that of the surface pinning. This was evident from the fact that the magnetization curves, M(H), were well described by the critical-state model without considering the reversible magnetization and the surface pinning effect. It was also found that the M(H) curves at various temperatures scaled when the field and the magnetization were normalized by the characteristic scaling factors H*(T) and M*(T), respectively. This feature suggests that the pinning mechanism determining the hysteresis in M(H) is unique below T = Tc.
Effect of Film Thickness on the Columnar Packing Structures of Discotic Supramolecules in Thin Films
Kim, Hyo-Sik,Choi, Sung-Min,Pate, Brian D.,Park, Po Gyu WILEY-VCH Verlag 2009 CHEMPHYSCHEM -WEINHEIM- Vol.10 No.15
<P>The effects of film thickness on the columnar packing structure of discotic supramolecules in a thin supported film have been investigated by grazing-incidence small-angle X-ray scattering technique using magnetically aligned cobalt octa(n-decylthio)porphyrazine (CoS10) films on octadecyltrichlorosilane (OTS)-functionalized substrates as model systems. Magnetically aligned CoS10 films with a range of film thicknesses (49–845 nm) form uniaxially oriented ‘edge-on’ columnar superstructures with their columnar directors perpendicular to the applied magnetic field. However, the orientational ordering of the columnar packing in the plane perpendicular to the applied magnetic field is strongly dependent on the film thickness. While being damped by the elasticity of the side chains of CoS10, the strong interfacial interaction at the film-substrate interface propagates up to 50–100 nm from the substrate, maintaining the orientation of columnar packing in the plane perpendicular to the applied magnetic field. When the distance from the film-substrate interface becomes larger than about 100 nm, symmetric tilting of columnar layer orientation, which saturates at 11.5°, occurs due to longitudinal edge dislocations induced by accumulated elastic deformation.</P> <B>Graphic Abstract</B> <P>Tilted alignment: Thin films (<100 nm) composed of uniaxially aligned columnar layers of a discotic mesogen on octadecyltrichlorosilane-functionalized solid substrates show undistorted two-dimensional columnar rectangular structures (see figure). In thicker films, symmetric tilting of the columnar layer orientation occurs as a result of longitudinal edge dislocations induced by accumulated elastic deformation. <img src='wiley_img/14394235-2009-10-15-CPHC200900464-content.gif' alt='wiley_img/14394235-2009-10-15-CPHC200900464-content'> </P>